This invention generally relates to stents and delivery systems for inserting stents into the body of a patient.
The male urethra is generally a tubular passageway extending from the bladder to the end of the penis. As urine travels from the bladder and out of the body, the urine passes through four sections of the urethra, referred to as the prostatic urethra, the membranous urethra, the bulbar urethra, and the pendulous or distal urethra. Surrounding the prostatic urethra and below the bladder is a prostate gland, which, among other functions, produces the fluid in semen.
A urological condition that some, mostly male, patients experience is blockage of the urethra. For instance, prostate enlargement, also known as benign prostate hyperplasia (BPH), is a common affliction experienced by some men. The condition involves swelling of the prostate, which prevents passage of urine from the bladder and consequently makes urination difficult or impossible. Prostate cancer is another affliction suffered by some men and may lead to many of the same symptoms as BPH.
Medical devices, such as urethral stents, have been developed to correct the problems of urine flow. Urethral stents are designed to hold open one or more of the sections of the urethra obstructing the flow of urine. Generally, these stents are made from a relatively small diameter tube or coil of a biocompatible material such as plastic.
A delivery system is often employed to deliver a urethral stent into the body of the patient. To deliver a urethral coil stent into the body, an existing delivery system typically winds or tightens the coil stent onto the exterior of a delivering catheter to reduce the diameter of the coil stent. The length of the wound stent is greater than the length of the stent in its expanded rest state. That is, prior to winding the coil stent onto the catheter for delivery into the body, and after release of the coil stent in (or outside of) the body, the length of the coil stent is less than when it is wound down onto the exterior of the delivery catheter. The winding thus both reduces the diameter of and extends the length of the coil stent.
The reduction of length that occurs upon deployment of a urethral coil stent makes it difficult to position accurately the coil stent within the urethra. The invention involves allowing a physician or other medical practitioner or professional to deploy and position a coil stent in a patient""s urethra without any substantial change in the length of the coil stent. Urethral coil stent delivery systems and related methods according to the invention allow accurate placement of the stent.
To avoid damaging surrounding structures (such as the external sphincter), a medical professional typically employs a scope (e.g., endoscope) to view the location at which the urethral coil stent will be placed. The medical professional can use the scope to line up the proximal end of the coil stent with the neck of the bladder. The length reduction that typically occurs when deploying a known urethral coil stent, however, frustrates the professional""s ability to place accurately the stent even when a scope is used.
In one aspect, the invention generally relates to a delivery system for placement of a stent within the body of a patient. The stent includes a coil, an elongated member, and a retaining structure. The coil defines a lumen and has an initial length when the stent is resting in an expanded equilibrium, or rest, state. Additionally, adjacent turns of the coil are positioned to substantially prevent tissue ingrowth through the turns and into the lumen when the stent is placed within the body. The retaining structure collapses and deforms a portion of the stent. In particular, the retaining structure includes one or more pins which collapse and deform at least a portion of the stent at particular pressure points. The stent, however, substantially retains its initial length. The elongated member is coupled to a distal end of the retaining structure to enable insertion of the retaining structure with the collapsed and deformed stent into the body. This insertion enables the collapsed and deformed stent to be deployed from the retaining structure and placed into the body of the patient while maintaining substantially its initial length.
Embodiments of this aspect of the invention can include the following features. The delivery system can also include a sliding member that slides through a lumen defined by the elongated member. The sliding member exerts a deploying force on the stent to deploy the stent from the retaining structure. The delivery system can also include a handle coupled to the elongated member. The handle may also be coupled to the sliding member to allow an operator of the delivery system to use the handle to slide the sliding member through the lumen defined by the elongated member. This exerts the deploying force on the stent.
In another aspect, the invention includes a method of loading a stent into a retaining structure. The method includes providing a stent having a coil and having an initial length when in an expanded rest state. The method also includes providing a retaining structure sized for insertion into the body and having one or more pins. The method includes inserting the stent into the retaining structure so that at least a portion of the stent becomes collapsed and deformed by one or more pins while the stent retains its initial length.
The method may also include the step of providing the stent which includes a membrane coating the coil. In another embodiment, the method includes inserting the retaining structure with the collapsed and deformed stent into the body. This enables the deployment of the deformed and collapsed stent from the retaining structure and placed into the body of the patient while maintaining substantially its initial length. In a further embodiment, the method includes the step of sliding a sliding member through a lumen defined by the elongated member to deploy the collapsed and deformed stent into the body of the patient.
The directional terms proximal and distal require a point of reference. In this document, the point of reference in determining direction is from the perspective of a patient. The term xe2x80x9cproximalxe2x80x9d refers to a direction that points into the patient""s body. The term xe2x80x9cdistalxe2x80x9d refers to a direction that points out of the patient""s body.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.